Aminyl and iminyl radicals from arylhydrazones in the photo-induced DNA cleavage

Photolytic cleavage of the nitrogen-nitrogen single bond in benzaldehyde phenylhydrazones produced aminyl (R2N*) and iminyl (R2C=N*) radicals. This photochemical property was utilized in the development of hydrazones as photo-induced DNA-cleaving agents. Irradiation with 350 nm UV light of arylhydrazones bearing substituents of various types in a phosphate buffer solution containing the supercoiled circular phiX174 RFI DNA at pH 6.0 resulted in single-strand cleavage of DNA. Attachment of the electron-donating OMe group to arylhydrazones increased their DNA-cleaving activity. Results from systematic studies indicate that both the aminyl and the iminyl radicals possessed DNA-cleaving ability.     

A novel approach towards studying non-genotoxic enediynes as potential anticancer therapeutics

A novel uracil-containing enediyne was synthesized by the fusion at N(1) and N(3) of uracil with an 11-membered cyclic enediyne. Compound was found to be stable against cycloaromatization at 80 degreesC. Thus, it did not cause DNA-damage. Unlike other alkylated uracil derivatives 2--6, highly strained uracil-containing enediyne was reacted with methyl thioglycolate at 25 degreesC to produce uracil () and linear enediyne. This reactivity toward a sulfhydryl group may play a significant role in the mechanism by which compound directed its cytotoxicity toward tumor cell lines. Tumor cells were found to be more susceptible to enediyne than normal human embryonic lung cells. A combination of with adriamycin or 1-(beta-D-arabinofuranosyl)cytosine resulted in synergistic anticancer activity against murine L1210 and P388 leukemias, Sarcoma 180, and human CCRF--CEM lymphoblastic leukemia. After treatment of Molt-4 cells with uracil-containing enediyne, light microscope examination demonstrated the presence of cell shrinkage and nuclear segmentation. Treatment of cultured Molt-4 human leukemia cells with enediyne resulted in a time-dependent depletion of glutathione (GSH) whereas the exposure of the cells to the GSH precursor N-acetylcysteine (NAC) resulted in a substantial suppression of this effect. As such, involvement of GSH depletion in the process of apoptosis may explain the mechanism of action of non-genotoxic enediyne against malignant tumor cell lines.     

Genetic assessment of the threatened microendemic <Emphasis Type="Italic">Pleurodeles poireti</Emphasis> (Caudata,Salamandridae), with molecular evidence for hybridization with <Emphasis Type="Italic">Pleurodeles nebulosus</Emphasis>

Short-range endemics are high-priority conservation targets, and valuable information for their management can be obtained from assessments of genetic diversity and structure, including potential hybridization with related species, and the investigation of factors shaping their patterns of occurrence. The Edough ribbed newt, Pleurodeles poireti, is restricted to the Edough Peninsula in Algeria, and listed as Endangered in IUCN’s Red List. Its range is completely surrounded by the more widespread, closely related, Algerian ribbed newt, Pleurodeles nebulosus. Here we examined patterns of genetic diversity and structure in P. poireti using mtDNA sequences of the ND4 gene and a suite of 12 polymorphic microsatellites in a sample of 193 individuals from 46 populations covering the whole range of P. poireti and neighboring populations of P. nebulosus. We also investigated the influence of environmental variables (climate, topography, soil texture and plant cover) on the patterns of occurrence of both species. Genetic data allow fine scale delineation of the ranges of the two species and provide evidence for hybridization in several localities in a broad area of overlap. Niche analyses indicate that P. nebulosus and P. poireti tend to occupy similar niches and that the hybrid zone is not associated to an ecotone. This suggests that the range boundaries of the two species may be constrained by reciprocal exclusion, although in the case of P. poireti there are additional environmental constraints. These distributional patterns could be explained by high occupation of habitats by P. poireti, hindering the penetration of P. nebulosus by a ‘density blocking’ effect.     

Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation

Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced dimerization of its two nucleotide-binding domains (NBD1 and NBD2), whereas gate closure is facilitated by ATP hydrolysis-triggered partial separation of the NBDs. This generally held theme of CFTR gating—a strict coupling between the ATP hydrolysis cycle and the gating cycle—is put to the test by our recent finding of a short-lived, post-hydrolytic state that can bind ATP and reenter the ATP-induced original open state. We accidentally found a mutant CFTR channel that exhibits two distinct open conductance states, the smaller O1 state and the larger O2 state. In the presence of ATP, the transition between the two states follows a preferred O1→O2 order, a telltale sign of a violation of microscopic reversibility, hence demanding an external energy input likely from ATP hydrolysis, as such preferred gating transition was abolished in a hydrolysis-deficient mutant. Interestingly, we also observed a considerable amount of opening events that contain more than one O1→O2 transition, indicating that more than one ATP molecule may be hydrolyzed within an opening burst. We thus conclude a nonintegral stoichiometry between the gating cycle and ATP consumption. Our results lead to a six-state gating model conforming to the classical allosteric mechanism: both NBDs and transmembrane domains hold a certain degree of autonomy, whereas the conformational change in one domain will facilitate the conformational change in the other domain.     

Differential expression of Bcl-2 and APP immunoreactivity after intrastriatal injection of MPP+ in the rat.

While there is growing evidence that Bcl-2 proto-oncogene and beta-amyloid precursor proteins (APP) are neuroprotective in function, our recent studies have demonstrated that Bcl-2 and APP may be co-expressed and co-regulated in retinal neurons or glia under normal or experimental conditions. Whether Bcl-2 and APP are functionally coupled in other neuronal systems is not clear. This issue was investigated further in the present experiments by examining the expression pattern of two molecules after unilateral intrastriatal injection of 1-methyl-4-phenyl-pyridinium (MPP(+)), a neurotoxic metabolite that selectively damages dopaminergic neurons. One hour to 2 months after MPP(+) injection into rat striatum, a significant increase in Bcl-2 expression was observed in distinct populations of neurons, astrocyte-like and OX-42-positive cells not only in traumatic regions but also in remote areas including the ipsilateral cortex and substantia nigra (SN). No detectable change was observed in the striatum, cortex or SN on the contralateral side of the brain. The immunoreactive pattern and time-dependent APP increase was similar to that of Bcl-2 in the severely injured striatum and cortex. However, an up-regulation of Bcl-2 expression, but not APP, appears in dopaminergic neurons in the ipsilateral SN pars compacta where there was retrograde degeneration. In contrast, APP immunoreactivity was decreased in the hippocampus following intrastriatal injury, whereas, no alteration in Bcl-2 expression was detected. The differential changes in Bcl-2 and APP expression in nigral neurons and some other brain tissues suggest that these proteins may not be co-regulated by a common mechanism, at least in certain neuronal pathways.     

A New Long‐Chain Alkene and Antituberculosis Constituents from the Leaves of Pourthiaea lucida

A new long‐chain alkene, dotriacont‐1‐ene ( 1 ), was isolated from the leaves of Pourthiaea lucida, together with twelve known compounds. The structure of this new compound was determined by NMR and mass‐spectrometric analyses. Among the isolated compounds, α‐tocospiro A ( 2 ), α‐tocopheryl quinone ( 4 ), and (E)‐phytol ( 5 ) exhibited antituberculosis activities (MICs ≤30 μg/ml) against Mycobacterium tuberculosis H₃₇Rv in vitro.     

New Pterosin Sesquiterpenes and Antitubercular Constituents from Pteris ensiformis

Two new pterosin sesquiterpenes, (2S)‐13‐hydroxypterosin A ( 1 ) and (2S,3S)‐12‐hydroxypterosin Q ( 2 ), were isolated from the whole plants of Pteris ensiformis, together with six known compounds. The structures of 1 and 2 were determined through extensive 1D/2D‐NMR and MS analyses. Compound 2 exhibited antitubercular activity (MIC 6.25 μg/ml) against Mycobacterium tuberculosis H₃₇Rv in vitro.     

Association of PON1 and PON2 Polymorphisms with PON1 Activity and Significant Coronary Stenosis in a Tunisian Population

PON1 and PON2 have attracted considerable attention as candidate genes for coronary heart disease because their enzymes function as key factors in lipoprotein catabolism pathways. We studied the distribution of PON1 and PON2 polymorphisms, including genotyping, lipid profile, and PON1 activity, and their association with PON1 activity and significant coronary stenosis (SCS) in a Tunisian population. PON1 activity was lower in patients with SCS than in controls. It increased with the R allele (QQ < QR < RR) in PON1-192 genotypes and with the L allele (MM < ML < LL) in PON1-55 genotypes. In the presence of metabolic syndrome and diabetes, PON1-192RR and PON2-311CC were associated with an increased risk of SCS and PON1-55MM seems to have lower risk. This association was evident among nonsmokers for PON1-55MM and among smokers for PON1-192RR and PON2-311CC. The GTGC haplotype seemed to increase the risk of SCS compared with the wild haplotype in a Tunisian population.